1. Field of the Invention
This invention relates to the side frame structure of a railcar truck assembly and more particularly, to an improved bearing adapter.
2. Description of Prior Art
The truck assembly of a railcar typically includes a pair of side frames on each side having downwardly opening jaws. A bearing adapter is vertically movable within the jaw and rests on a roller bearing that rotatably carries a wheel axle. The bearing adapter is mounted on a side frame by a mating lug arrangement to inhibit movement in other directions within the jaw.
It is long been an objective to support the adapters on the side frames with minimum lateral clearance to prevent relative movement between the truck and car frame. Such elimination of lateral movement of the adapter was intended to provide better wear characteristics and other alleged design advantages. Accordingly, prior traditional designs for adapter castings used in truck assemblies have stressed the benefits of minimizing lateral movement of the adapter relative to the side frame, as it sits upon the roller bearing, to the extent possible for optimum truck operation.
In recent years, however, the advantages of uncoupling the wheel set from the railcar body have become recognized in the railcar industry. Accordingly, there is a important need to provide means for effectively accomplishing such a uncoupling effect in rail cars as now found desirable.